[SOLVED] Use specific protobuf version when multiple versions are installed

Use specific protobuf version when multiple versions are installed

I am trying to compile the gazebo example provided by PX4, according to PX4's instructions. I am working on Ubuntu-18.04.

When running the command: make px4_sitl gazebo, following error occurs:

...
In file included from Range.pb.h:27:0,
                 from Range.pb.cc:5:
/usr/include/gazebo-9/gazebo/msgs/quaternion.pb.h:12:2: error: #error This file was generated by a newer version of protoc which is
 #error This file was generated by a newer version of protoc which is
  ^~~~~
/usr/include/gazebo-9/gazebo/msgs/quaternion.pb.h:13:2: error: #error incompatible with your Protocol Buffer headers. Please update
 #error incompatible with your Protocol Buffer headers.  Please update
  ^~~~~
/usr/include/gazebo-9/gazebo/msgs/quaternion.pb.h:14:2: error: #error your headers.
 #error your headers.
  ^~~~~
...

Piecing the error message back together gives: This file was generated by a newer version of protoc which is incompatible with your Protocol Buffer headers. Please update your headers.

I have two different protoc binaries on my machine:

/usr/bin/protoc (3.0.0), the minimum version required
~/catkin_ws/devel/bin/protoc (2.6.0), which is too old and used by default

How can I make sure the first version is used? I tried this: export PATH=/usr/bin:$PATH to make sure the right compiler is found first but I would also probably need to indicate to use the right headers, hence the ones in /usr/include/google/protobuf instead of ~/catkin_ws/devel/include/google/protobuf. However, I am not sure about how to proceed.

Solution

Ok, so simply making the bad path invalid (modified it) forced make to use the right compiler version since it could not find the wrong version anymore.

Weird to see that putting the path of the correct version first in the PATH variable did not seem to have any effect.